1. Field of the Invention
The field of the invention is that of the control of access to signals transmitted within heterogeneous networks including at least one basic network and at least one sub network.
The invention can be applied especially, but not exclusively, to a heterogeneous network of digital buses, in which the sub-networks are digital buses. It may be recalled that a heterogeneous network of digital buses is called “heterogeneous” because certain interconnections between digital buses are made directly, through homogenous bridges, while other interconnections between digital buses are made through at least one basic network, through heterogeneous bridges.
More specifically, the invention relates to a method of inserting information for the control, by a destination node, of the broadcasting of a data stream crossing a basic network of a heterogeneous network as well as a method for the processing of this information.
The invention can be applied especially, but not exclusively, in the special case where the heterogeneous network of digital buses is a home audiovisual network, whose basic network is a switched network of the type comprising a plurality of nodes connected together by a plurality of links.
Such a home audiovisual network enables the interconnection of analog and/or digital type audio and/or video terminals (also called devices) so that they may exchange audiovisual signals. The terminals belong, for example, to the following non-exhaustive list of devices: television receivers (using satellite, RF channels, cable, xDSL and other means), television sets, video tape recorders, scanners, digital camcorders, digital cameras, DVD readers, computers, personal digital assistants (PDAs), printers, etc.
In this particular case, the links are, for example, of the type enabling two-way data transfers according to the IEEE 1355 standard. It may be recalled that the IEEE 1355 standard is defined by the reference Std 1355-1995 Standard for Heterogeneous InterConnect (HIC) (Low Cost Low Latency Scalable Serial Interconnect) (aka ISO/IEC 14575 DIS).
Furthermore, also in this particular case, the digital buses are, for example, IEEE 1394 type digital bus networks. It may be recalled that the IEEE 1394 standard is described in the following reference documents: “IEEE Std 1394-1995, Standard for High Performance Serial Bus and “IEEE Std 1394a-2000, Standard for High Performance Serial Bus (Supplement)”. A third document “IEEE P1394.1 Draft 0.17 Standard for High Performance Serial Bus bridges” describes the way to connect different IEEE 1394 type buses.
2. Description of the Prior Art
In general, a heterogeneous network of this kind works as follows: a connection is set up, generally through a plurality of nodes of the basic network, between a destination terminal (or listener) that wishes to receive audiovisual signals and an entry terminal (or talker) that can give it the signals.
It is assumed that the digital buses convey first packets (for example IEEE 1394 packets) and the basic network conveys second packets (for example IEEE 1355 packets). Thus, the data stream concerned is conveyed on the digital buses by first packets. To enable the crossing of the basic network by this data stream, the entry node divides and/or concatenates these first packets to encapsulate them in second packets. Conversely, the destination node de-encapsulates the contents of the second packets that it receives, and then generates first packets.
Typically, the basic network is a switched network conveying second packets whose size is variable and determined by quality of service (QoS) imperatives. Since the second packets are variably sized, it is impossible to ensure that the first and second packets will be aligned.
A few elements of the terminology used hereinafter in the description shall now be specified.
The term “entry node” or “talker node” designates the node to which the entry or talker terminal is connected, directly or through a digital bus.
In general, the entry node does not comprise means for the reception and/or reading of source signals (originating from outside the network). It receives audiovisual signals coming from the entry terminal and introduces them into the home audiovisual network. The term “entry terminal” is understood to mean, for example, a digital camera, a digital camcorder, a digital output DVD player or any analog device seen through an analog/digital converter.
It will be noted however that, in one particular case, the terminal is integrated into the entry node, which is called a “source node”. Thus, it is assumed that the source node comprises means for the reception and/or reading of source signals (originating outside the network) and means for the transmission of these source signals, in the form of the above-mentioned audiovisual signals, to the destination node. Typically the source node (also called a “Tuner Unit”) includes a television receiver, for example in France a “TPS” (registered mark) receiver. It enables the direct introduction into the network, in digital form (generally encoded in the MPEG2 format) of source signals given by an operator and containing television programs.
To put it briefly, in the particular case mentioned here above, the following four situations can be distinguished on the entry node side:                the entry terminal is a digital type of terminal, connected to the entry node through a digital bus (entry sub-network). It directly generates the data stream in the form of first IEEE 1394 packets;        the entry terminal is an analog type terminal, connected to an independent adapter, which is itself connected to the entry node through a digital bus (entry sub-network). The adapter enables the conversion, into first IEEE 1394 packets, of the data stream generated in the form of analog signals by the entry terminal;        the entry terminal is an analog type terminal directly connected to the entry node. This node integrates the above-mentioned adapter;        the entry terminal is integrated into the entry node. This entry node which, in this particular case, is called a “source node” directly generates the data stream in the form of first IEEE 1394 packets.        
The term “destination node” or “listener node” designates the node to which the destination or listener terminal is connected, directly or through a digital bus.
To put it briefly, in the particular case mentioned here above, the following four situations can be distinguished on the destination node side:                the destination terminal is a digital type of terminal, connected to the destination node through a digital bus (destination sub-network). It directly receives the first IEEE 1394 packets generated by the destination node and representing the data stream;        the destination terminal is an analog type terminal, connected to an independent adapter, which is itself connected to the destination node through a digital bus (destination sub-network). The adapter enables the conversion, into analog signals, of the first IEEE 1394 packets generated by the destination node and representing the data stream;        the destination terminal is an analog type terminal directly connected to the destination node. This node integrates the above-mentioned adapter;        the destination terminal is integrated into the destination node. This destination node directly processes the data stream in the form of first IEEE 1394 packets.        
The control of access to the signals transmitted within a heterogeneous network is an essential question. Indeed, in a home audiovisual network, for example, there are novel technologies which now enable access to numerous multimedia contents (audio and/or video and/or text contents). Through numerous stream connections within the network, all these multimedia contents can very easily be shared within a home. Each family member can thus access data from any room in the house in which there is a node of the network. It can easily be seen, however, that certain persons should be prevented from accessing programs unsuited to them. For example, children have to be barred from seeing films depicting violence. A control system (hereinafter also called a “parental control system”) is therefore necessary.
Now, to date, there is no satisfactory selective technical solution for setting up a parental control system such as this, especially in a home audiovisual network.
In the prior art, there is a parental control technique known from the U.S. Pat. No. 6,009,433 in which:                on the source equipment side, parental control information is inserted directly into the MPEG2 data packets;        the MPEG2 data packets are transmitted through the transmission network; and        on the destination equipment side, the parental control information is read and processed in order to decide on the processing to be applied to the payload data (typically, whether or not to restitute a video stream on a television set).        
This known technique is not suited to the present context, in which the signals are transmitted within a heterogeneous network (typically a home audiovisual network).
Indeed, if the above-mentioned known technique were to be transposed into the present context of a heterogeneous network, the parental control information would be inserted into the first packets (for example, IEEE 1394 type packets). Now, a modification of high-level data of this kind would be complex and costly to achieve.
Furthermore, all the destination terminals would have to be equipped with means for reading and processing this parental control information. This would appear to be hardly acceptable especially for reasons of cost.
Furthermore, this known technique does not provide for optimal management of a multicasting situation in which one and the same stream is given to several destination terminals (for example, to television sets located in different rooms). Indeed, this technique gives no information on the way to synchronize several destination terminals successively on one and the same data stream.